5 files changed, 7 insertions, 5 deletions
diff --git a/test/ruby/test_module.rb b/test/ruby/test_module.rb
index 59b3df5f04..98c9128406 100644
--- a/test/ruby/test_module.rb
+++ b/test/ruby/test_module.rb
@@ -1046,6 +1046,7 @@ class TestModule < Test::Unit::TestCase
 
   def test_attr_obsoleted_flag
     c = Class.new do
+      extend Test::Unit::Assertions
       extend Test::Unit::CoreAssertions
       def initialize
         @foo = :foo
diff --git a/tool/lib/core_assertions.rb b/tool/lib/core_assertions.rb
index 5720eb1ac3..f94a5dff66 100644
--- a/tool/lib/core_assertions.rb
+++ b/tool/lib/core_assertions.rb
@@ -25,9 +25,7 @@ module Test
 
     module CoreAssertions
       require_relative 'envutil'
-
       require 'pp'
-      include Test::Unit::Assertions
 
       def mu_pp(obj) #:nodoc:
         obj.pretty_inspect.chomp
diff --git a/tool/lib/test/unit/assertions.rb b/tool/lib/test/unit/assertions.rb
index db8128536c..bdb25d0d85 100644
--- a/tool/lib/test/unit/assertions.rb
+++ b/tool/lib/test/unit/assertions.rb
@@ -1,5 +1,4 @@
 # frozen_string_literal: true
-require_relative '../../core_assertions'
 require 'pp'
 
 module Test
diff --git a/tool/lib/test/unit/testcase.rb b/tool/lib/test/unit/testcase.rb
index 6ce9f5940d..ea3092a4b3 100644
--- a/tool/lib/test/unit/testcase.rb
+++ b/tool/lib/test/unit/testcase.rb
@@ -1,5 +1,6 @@
 # frozen_string_literal: true
 require 'test/unit/assertions'
+require_relative '../../core_assertions'
 
 module Test
   module Unit
@@ -143,6 +144,9 @@ module Test
     # See MiniTest::Assertions
 
     class TestCase
+      include Assertions
+      include CoreAssertions
+
       include LifecycleHooks
       include Guard
       extend Guard
@@ -332,8 +336,6 @@ module Test
 
       def teardown; end
 
-      include CoreAssertions
-
       def on_parallel_worker?
         false
       end
diff --git a/tool/test/webrick/utils.rb b/tool/test/webrick/utils.rb
index 85fc2bc641..a8568d0a43 100644
--- a/tool/test/webrick/utils.rb
+++ b/tool/test/webrick/utils.rb
@@ -36,6 +36,8 @@ module TestWEBrick
   RubyBinArray << "-I" << "#{File.dirname(EnvUtil.rubybin)}/.ext/#{RUBY_PLATFORM}"
 
   require "test/unit" unless defined?(Test::Unit)
+  include Test::Unit::Assertions
+  extend Test::Unit::Assertions
   include Test::Unit::CoreAssertions
   extend Test::Unit::CoreAssertions